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Choosing a Sports Drink: The Importance of ElectrolytesAs we exercise, we increase the amount of electrolytes that our body requires to operate to the limits of its potential. During long (3hr +) bouts of exercise, we must be attentive to these changing nutritional requirements. It is important to choose a sport drink that meets these changing needs.
The five most important non-caloric ingredients in sports drinks (3 electrolytes, an anti-oxidant and an amino acid) are listed below. If at all possible, choose a sport drink that has all these electrolytes and nutrients. It is tricky to obtain a powered sport drink with vitamin E. The purpose of the Vitamin E is to serve as an anti-oxidant, finding and destroying free radicals. Luckily, vitamin C works just fine for this purpose. We recommend that you choose a sports drink with over 500mg Vitamin C per liter of sports drink. Calcium is one of the most important nutrients for athletes. The recommended dietary intake ranges from 1,000 to 1,500 mg/day depending on age and gender. Fewer than half of the general population consume 1,000 mg of calcium daily. Athletes consume a slightly larger amount of calcium than the general population but only because we eat more. All athletes should make sure they get 1,200 to 1,500 mg of calcium daily from food or supplements. Athletes training more than 10hrs/week should eat even more. Calcium should be an ingredient in every athletes sports drink.
Potassium is a mineral and is responsible for regulating total body water and stabilizing contractions (both controlled and automatic). A deficiency of potassium (hypokalemia) can manifest as weakness, fatigue, confusion, heart irregularities, and sometime cause problems in muscular coordination. Insufficient potassium can also exaggerate the effects of a lack of available sodium. The first sign of a potassium deficiency is usually a generalized weakness - not something you wish to experience during an Ironman or marathon. These events are tough enough without throwing weaknesses caused by electrolyte deficiencies into the picture.
Most people get sufficient potassium if they eat a reasonably healthy diet -- one that includes fresh fruits and vegetables and is low in sodium. Mineral imbalances can occur from starvation diets, but more commonly results from excessive fluid loss from sweating, diarrhea, or the use of diuretics and laxatives.
People who exercise heavily, and therefore sweat heavily, have higher potassium needs; they may need to take supplements to balance the electrolyte levels, or to bulk up their menus with high potassium foods. On the other hand, people who suffer from some diseases, including diabetes and renal (kidney) failure can no longer metabolize minerals properly and need to guard against getting too much in their diet.
Potassium is mainly lost through sweat and urine. In a study of athletes running 40 minutes at 70 degrees Fahrenheit, potassium loss was estimated at 435 mg/hour. Potassium is lost as cells release potassium into the bloodstream during exercise.
Based on this rate of potassium loss, supplementation after both short and long events is warranted. For post exercise replacement, athletes should take potassium supplements of about 435 mg/hour of exercise or 200 mg/kg of weight loss. As much as 150 mg/hour during activity can be tolerated by most athletes. Supplement potassium cautiously because too much too quickly can cause cardiac arrest.
Supplementing with potassium during training does increase markers of recovery, primarily serum lactate and muscle hydration, but does not aid performance. Potassium supplementation does however, increase performance by increasing the recovery rate. Athletes recover faster from workouts and possible improve move as a direct result. Sodium has been in the press a great deal lately. Sodium is important because it enables ATP generation. But this is not what sodium (a.k.a salt) is famous for. Salt helps cells retain water and prevents dehydration. For events lasting longer than five hours, especially in hot weather, dangerously low sodium is a real concern. Anyone out for more than a few hours, especially on a warm day, should make sure to get some salt from snacks and fluid-replacement drinks.
However, it should be noted that salt supplementation is not really necessary for endurance events under 4 hrs. Loss of sodium through sweat can become a problem during ultra-endurance events (or continuous exercise that lasts over 4 hours). Risk groups are:
- Those who sweat profusely and only partially replace this loss with water or a low sodium drink (otherwise known as hyponatraemic dehydration)
- Those who have a low sweat rate who consume excess amounts of water in effect diluting their sweat (water intoxication). The first sports drinks were introduced in the 1970's and contained high levels of sodium to mimic the composition of sweat. It was originally thought that significant levels of sodium were lost in sweat and must be replaced, which we now know is not true (except in the extreme cases mentioned above.) Why then are sodium and other minerals added to sports drinks ?
The reasons are outlined below:
- Sodium increases the speed at which fluid and glucose is absorbed into the body. This means that we are less susceptible to dehydration and thus can exercise for longer or at a higher intensity.
- Sodium improves palatability as it offsets the sweetness of the added sugars. There is also some evidence that after exercise and when dehydrated most people have a preference for a slightly salty tasting beverage
- Sodium and other electrolytes do need replacing in ultra endurance events over 4 hours.
A prospective study was performed on 36 athletes during a three- to four-hour triathlon and 64 athletes at an ironman race, which lasts between nine and 15 hours. No athletes were hyponatremic (low sodium levels) after the shorter race, but 27 percent were hyponatremic following the Ironman™. An average of 17 percent of the Ironman™ participants required medical attention, most for hyponatremia. Extrapolated from that study, athletes should aim for 80 to 100 mg sodium per quart of hydrating beverage and 100 to 300 mg sodium per hour from other sources for events lasting longer than four hours. Vitamin E is of the most effective antioxidants in existence.
Aerobic athletes probably have an increased need for this vitamin because their cells undergo more oxidative damage than their sedimentary counterparts. Research shows athletes have less cellular damage when they ingest more vitamin E. Aerobic exercise places additional demands on the molecular free radical scavengers of the body, and vitamin E is a well-known scavenger.
In a study of 30 top-class cyclists, five months of supplementation with natural vitamin E (alpha-tocopherol) at an 800-IU daily dose significantly decreased markers of oxidative damage to muscle tissue. However, vitamin E did not benefit athletic performance.
Studies evaluating vitamin E as an ergogenic, or performance aid, show no benefit. One possible exception is at higher altitudes where oxidative stress is more intense. A group of six mountain climbers took 400 mg synthetic vitamin E (dl-alpha-tocopherol acetate). During exertion at altitude, they showed less output of pentane and lactic acid-both markers of oxidative damage, but not suggestive of improved athletic performance. The athletes also showed a statistically significant increase in anaerobic threshold compared to a placebo group.
The amount of vitamin E necessary to benefit athletes is not obtainable through diet. The jury is still out on natural vs. synthetic vitamin E, but endurance athletes should take 400 to 800 IU/day.
It is not possible to add vitamin E to powdered sports drinks, but it is very important to include antioxidants in a sports drink. As a substitute, it is sufficient to consume 100mg of Vitamin C/hour. However, care should be taken because the consumption of Vitamin C in a powdered form can be acidic and thus hard on tooth enamel. Glutamine is an amino acids and found in most sources of protein. Both Whey, Soy and Hemp Protein are excellent sources of Glutamine. The RDA for protein is 60 mg per day for adults (specifically 0.8 g/kg of body weight/day). This recommendation, however, is based on the needs of sedentary individuals. Studies indicate that protein needs increase during strenuous activity, to between 1-2g/kg of weight/day.
Athletes who train strenuously for competition have greater nutritional needs than sedentary people. Adequate nutrients can mean quicker recovery time, lower infection rates, less fatigue, and ultimately, can help athletes reach their desired performance levels. Some of these nutrients (salt, Vitamin E/C, Glutamine) must be ingested during long bouts of intense exercise. A convenient means of obtaining these nutrients is to choose a sport drink specifically tailored to your nutritional needs. When choosing a sports drink, try to obtain one such as at www.custom-sports-drinks.com.